A philosopher once asked, "Are we human because we gaze at the stars, or do we gaze at them because we are human?" Pointless, really… "Do the stars gaze back?" Now that’s a question.
-Narrator, "Stardust"

Late last night, the NASA mission Stardust flew within 178 km (110 miles) of the nucleus of the comet Tempel 1, seeing it up close for the first time since July 2005! Here’s one of the better images from closest approach:

To give you an idea of what you’re seeing here, the comet is roughly 7.6 x 4.9 kilometers (4.7 x 3.0 miles) in size.

So, why did NASA fly Stardust past this comet? Ah, set the way-back machine for 5.5 years ago…
In July 2005, NASA’s Deep Impact space probe flew past the comet Tempel 1. As it did, it slammed an 370 kilogram (800 pound) block of copper into the comet at a speed of 10.2 km/sec (6.3 miles per second). The purpose was to create a crater on the surface and excavate deeper material, allowing scientists to see what lay beneath. When the impactor hit, the energy released was equivalent to nearly 5 tons of TNT exploding! And while some amazing images were returned, the expanding cloud of debris blocked the best views, and so it wasn’t possible to get all the data they wanted.

The Stardust probe, meanwhile, was originally launched to collect samples from the comet Wild-2 and return them to Earth using an ejectable return container. The main probe sailed on, and engineers repurposed it to swing by Tempel 1 to see if any new images could be taken. And now, nearly six years later, the renamed Stardust-NeXT (Stardust-New Exploration of Tempel) mission has succeeded!

The whole point here was to see the impact crater from 2005, and Stardust was able to do that. It’s difficult to see in these images here, but Pete Schultz, an impact specialist with the mission, said the crater is about 150 meters across and has a central peak, indicating material fell back to the comet. The crater wasn’t as obvious as expected, but is about the right size given the impactor speed, mass, and angle of impact.

On the right is an image from Stardust near closest approach, and on the left is one from Deep Impact, which I rotated to match up the orientation. The angle of observation was different for the two spacecraft but you can see some of the same features. For example, on the DI image you can see two large craters on the left, and those are also in the Stardust picture fairly well centered. It so happens that the impactor from DI hit between those two craters, very close to the one on the left. As I mentioned, the new crater is extremely difficult to see — during the press conference, I couldn’t see it even when the location was pointed out!

Comets don’t have weather like planets do — no atmosphere! — but their icy surfaces get modified as they approach and recede from the heat of the Sun. Other Stardust images do show some changes to the comet’s surface! As the scientists get more of a chance to compare before-and-after shots, they’ll be able to see even better how this tiny world has changed since we visited it last.

We really are some clever little bits of carbon aren’t we? Hurtling a small device at over 10km per second halfway across the solar system to come within spitting distance of a 7km long chunk of rock and ice moving at very high speed itself… and do it not once but twice with the same vehicle. Add to that being able to take highly detailed photos of the event and send them back across the blackness of space to our tiny little ball of water and dirt…. Simply jaw dropping.

Now, if we can just get a large enough sample of that ice back here… I’m in the mood for a Comet Icee! 😉

The impact site is between the craters if you say so. Not much to see with the unaided eye, but cool nontheless. The deep impact projectile probably felt like a bug hitting the windshield to the comet.

Superluminous news – and images! Congratulations & thanks to all those involved.

Valentine’s encounter? (On the youtube animation by Ian O’Neill.)

I thought the renamed name was Stardust-NeXT not Valentine! 😉

Also I rather wish they wouldn’t do that renaming thing they seem to keep doing now. (Eg. Deep Impact -> EPOXI) What’s wrong with just calling it Stardust still & simply saying this is it’s extended mission instead? Minor gripe but still.

from GLAST or the Japanese changing Muses-C into Hayabusa once that was successfully launched. Those are apt & great too and were improvements on their original “working titles” in my view. I just don’t see the point or value in making up the new acronyms for the spaceprobe names for the extended missions. (Eg. EPOXI, Stardust-NexT.) It just seems to be unneccesary & potentially confusing.

After reading all the horrible political and international news today and having a rousing discussion on it that was just sad, I hit this article, and all of my responses were simply links of this post and “Its a picture of a f-ing comet”.

These images are absolutely amazing and have reduced me to a child-like state of wonder and awe. Utterly amazing what we can do, and what the universe holds.

@29 Robert: I was wondering that too.
I would guess that it’s because copper is spectroscopically distinct from the stuff they expect to find in the comet, so it wouldn’t mess up their readings as they’re doing a spectral analysis of the plume of stuff coming away from the impact. I don’t know about lead, but iron is pretty common in some asteroids, so there’s a possibility that some was deposited in/on the comet, and steel contains carbon, so both are things you wouldn’t want to fire at a comet if you wanted to know exactly what its composition is.
For all I know, it could be something completely different, though. Maybe copper is more ductile and they wanted the impactor to flatten out as it penetrates instead of fragmenting. Just guesses…